The present invention relates to an improved nozzle arrangement for a jet drilling apparatus. The invention particularly relates to such an apparatus as applied for cleaning of surface and subterranean pipes and boreholes for hydrocarbon reservoir exploration and production, more particularly to the removal of scale and other deposits from the inside diameter of well tubulars and boreholes.
It has been common practice for many years to run a continuous reeled pipe (known extensively in the industry as xe2x80x9ccoil tubingxe2x80x9d) into a well to perform operations utilising the circulation of treating and cleanout fluids such as water, oil, acid, corrosion inhibitors, hot oil, nitrogen, foam, etc. Coil tubing, being continuous rather than jointed, is run into and out of a well with continuous movement of the tubing through a coil tubing injector.
Coil tubing is frequently used to circulate cleanout fluids through a well for the purpose of eliminating sand bridges, scale, and similar downhole obstructions. Often such obstructions are very difficult and occasionally impossible to remove because of the inability to rotate the coil tubing and drill out such obstructions. These well tubulars vary from unperforated and perforated pipe, large diameter casing, production tubing, and slotted or wire-wrapped well liner. Well tubulars often become plugged or coated with corrosion products, sediments and hydrocarbon deposits. The deposits may consist of silicates, sulphates, sulphide, carbonates, calcium, and organic growth.
It is desirable to perform drilling type operations in wells through use of coil tubing which can be run into and removed from a well quickly in addition to performing the usual operations which require only the circulation of fluids. The same types of well servicing can also be performed with various small diameter work strings. The present invention may be used with such work strings and is not limited to coil tubing.
High pressure fluid jet systems have been used for many years to clean the inside diameter of well tubulars. Examples of such systems are disclosed in the following U.S. Pat. Nos. 3,720,264, 3,811,499, 3,829,134, 3,850,241, 4,088,191, 4,349,073, 4,441,557, 4,442,899, 4,518,041, 4,919,204, 5,181,576 or 5,337,819.
In U.S. Pat. No. 3,720,264, there is disclosed a jet tool for cleaning a liner. The jet tool includes three pairs of jet nozzles arranged in a staggered manner with each pair of nozzles slightly rotated with respect to the others.
In U.S. Pat. No.4,442,899, the nozzles are circumferentially spaced from each other about 90 degrees and separated such as to form a spiral.
U.S. Pat. No. 5,337,819 discloses a washing tool for removing internal deposits in tubing parts and components in wells for oil and gas production. The known tool comprises an actuation sleeve which has lateral dimensions related to the deposits to be removed. The sleeve actuates a valve to discharge a fluid jet through layers of circumferentially arranged discharge nozzles.
In view of the above cited prior art, it is an object of the invention to provide an improved fluid jet cleaning tool to remove scale and other deposits from the inside diameter of tubulars and boreholes for the exploration and production of hydrocarbon reservoirs. It is a particular object of the invention to provide a novel nozzle arrangement for such a fluid jet cleaning tool.
According to the present invention there is provided a fluid jet cleaning apparatus for cleaning of tubulars and boreholes for hydrocarbon reservoir exploration and production, said apparatus comprising a rotatable nozzle head including less than five axially separated nozzles mounted on a part of a lower end of a hollow tubular.
It has been recognised that the number of nozzles of a well cleaning tool can be reduced to less than five, preferably less than four without significant loss of performance.
Furthermore, it was found that the efficiency of the tool can be increased over tools with an equal number of nozzles by axially separating the nozzles. The preferred axial separation between two adjacent nozzles is larger than 0.5 times the nozzle diameter, but smaller than 20 times, more preferably 10 times, the nozzle diameter.
The preferred angular separation is either 180 degrees in case of two nozzles, 120 degrees in case of three nozzles or for four nozzles, a separation of 180 degrees between a pair of nozzles with the second pair preferably rotated by 90 degrees with respect to the first pair of nozzles.
The cleaning tool may also comprise a gauge defining sleeve with an essentially annular edge of a width of less than 10 mm, preferably 5 mm. The nozzle located closest to the sleeve is targeted at an area of the tubular or wellbore immediately below the sleeve member.
These and other features of the invention, preferred embodiments and variants thereof, and advantages will become appreciated and understood by those skilled in the art from the detailed description and drawings following below.